System for producing refrigeration



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-H. i5. EDWARDS SYSTEM, FOR PRODUCING REFRIGERATION Filed Nov. 20, 1933Patented Jan. 29, 1935 I I I UNITED STATES PATENT OFFICE 1,989,636SYSTEM FOR PRODUCING REFRIGERATION Harry D. Edwards, Larchmont, N. Y.,assignor to The Linde Air Products Company, New York, N. Y., acorporation of Ohio Application November-.20, 1933, Serial No. 698,794In Cuba April 23, 1932 17 Claims. (01. 62-123) This invention relates toa system for producplified in the construction hereinafter set forth ingrefrigeration, and more particularly to an and the scope of theapplication of which will be improved method and apparatus for producingindicated in the claims.

refrigerating effects by compressing and expand- For a fullerunderstanding of the nature and ing air to be separated into oxygen andnitrogen objects of the invention, reference should be had 5constituents by rectification. to the following detailed descriptiontaken in con- The invention has for its object generally an nection withthe accompanying drawing, in improved construction and'arrangement ofparts which: in gaseous cooling and/or separating systems Fig. 1 is aschematic view partly in section and which are eflicient, economical andreadily manupartly in elevation showing means for accom- 1'0 factured.plishing thermodynamic operations on a gaseous More specifically, theinvention has for its obmedium used in producing refrigeration in acjectthe provision of an arrangement, in which a cordance with the invention.gaseous medium is compressed, cooled and ex- Fig. 2 is a fragmentaryview showing in detail panded, for utilizing the expansion to doexternal regulating mechanism of a character employed 15 work fordriving compression machinery in a in conjunction with certain expansionmachinery manner which is advantageously reliable, efiishown in Fig. 1;and cient and economical in operation. Fig. 3 is a fragmentary sectionalview taken Another object is to separate the compression on the line 3-3in Fig. 2.

machinery which preliminarily compresses the The use of expansionengines for producing low 20 gaseous medium to be supplied torefrigerating temperatures is well known in the art of refrigapparatus,such as that in which a liquefied gas eration, and it has heretoforebeen proposed to is produced, into main compressing stages and utilizethe energy made available-by the expanboosting compressing stages andutilize expansion sion of the medium supplied to such engine. No

of at least a part of the compressed medium by satisfactory arrangement,however, has been doing external work to operate the boosting stagesheretofore proposed for employing such engines in a manner which tendsto accommodate itself in gas liquefaction systems of the present type,tochanging loads without undue strain and waste. because the properpower distribution was not It is also an object to provide a system forproclearly recognized. In general, either the motive 0 ducingrefrigeration having both throttling and power available was notproperly'accommodated engine expanding devices so constructed, relatedto variations in load, or a proper proportion of and proportioned that,when there is a tendency the load was not allocated to the expansion forthe refrigeration effects of the throttling and engine.

engine expanding devices to become unbalanced In the production of gasesseparated from the and supply refrigeration in disproportionateatmosphere, particularly in the production of amount, there is inherentcapability in the sysoxygen,- expansion engines, geared to various temof restoring the balance, whereby t system fixed loads, have been triedto provide some reprovided is self-regulating. frigeration. Changingconditions in the refrig- S ill an h Obj is 11 p v a system of erationto be provided, however, made the operathe character indicated withexpansion means tion of uch engines irregular and interruptions 4arranged to accomplish a p O t expansion by and cessation of service notinfrequently occurred. d in ter W h o tling and the balance Twodifferent methods of gearing such engines to y doing external Work in apredetermined ratio the load were, in general, practiced; for example,to the former; arr m n eing made to vary the engine was geared or beltedto a compressor the xpan n doing external w ti ly which was positivelydriven or assisted by an elec- 45 as als man l y, to eeeemmedate it to vn tric motor, or similar prime mover, so as to be run refri erati n arefrigeration requirements at a constant speed, or it was geared todrive an Other Obje ts of t invention Will in P he electric generatorwhich was connected to a bank. obvious and w in Part appear he einaft oflamps or other resistance load. which wasted This application is acontinuation in part of or dissipated the energy of expansion.- In cases50 my eepending application which issued y 29, where the first methodwas practiced, the varia- 1934 as Pate o. 1,960,623- tions in the loadimposed such service stresses on The invention acc r in y p i es thefea-. the gearing or belting that it'was'relat'ively short tures ofconstruction, combination of elements, lived. In practice, the secondmethod was genand arrangement of parts, which will be exemerallypreferred. 5;,

In the practice of the present invention, the compressing machinery isdivided into a main part which does the main work of compression andinto a boosting part which compresses to a still higher pressure than inthe main part and has an expansion engine geared to drive the latterpart, or booster; the energy for driving the main part beingindependently supplied. This permits the regulation of the expansionengine to respond to variations in the refrigeration load as well asavoiding undue strains in the connection gearing. Also, in the preferredform, it is proposed to expand a part of the gas at high pressure bythrottling at low temperatures to produce a high quality refrigeratingeflect under the Joule-Thomson principle, and to expand the balancethrough the expansion engine with external work usefully applied in thebooster, to give a lower quality but large quantity refrigeratingeffect. In the system where the two effects are utilized, arrangementsare provided to control the ratio between the volumes separatelyexpanded, the two expansion means being operated in parallel.

The present invention provides means for counteracting tendencies towardvariation in speed of the booster-expander and to maintain asubstantially constant refrigerating effect in the gases delivered bythe system to a rectifying column. It also provides a balance in bothrespects automatically and in spite of variations in the conditionsaffecting the system. The. factors which effect the accomplishment ofthese ends include, in the embodiment shown, a substantially constantrate of delivery from the main compressing means to the booster, theoperation of the booster by other means, namely, an expansion enginedevice coupled to the booster and driven by the power produced in theexpansion of a portion only of the booster output, a ratio of expansionin the expansion engine substantially greater than the ratio ofcompression in the booster, and themaintenance of open and communicatingpassages from the outlet of the booster to the throttling valve and tothe intake of the expansion engine, so that the pressure will rapidlyequalize between these points.

There are inherent difficulties in obtaining the desired equalization ina system using a throttling valve, as here proposed, since thethrottling valve may clog and interfere with the desired flow of gasinto the rectifying column. Pressure within the passages whichcommunicate with the throttling valve, in consequence, tends to rise andproduce a slight increase in the power available to the expander. Thistends to cause the expansion engine 'to' increase its speed. However,the mechanical coupling would cause an equal tendency to increase thespeed of the booster, which would tend to diminish the pressure in thegas which is'being supplied to the booster at a constant rate andincrease the ratio of booster compression. Thus the added work imposedupon the booster would absorb the tendency of the expander to increasespeed and quickly and automatically restore the desired normal balance.

If, on the other hand, the flow of throttled gas is increased as, forexample, by the removal of an obstruction, the first result is a reducedpressure in the lines which are connected with the throttling valve, anda slight reduction in the power available to the expander with atendency for the latter to reduce its speed. Again, this tendency isoffset by the mechanical connection to the booster and the reduction inbooster compression ratio which always results when the speed of thebooster is so reduced as to increase the pressure in the gas which isbeing supplied to the booster from the constant speed compresors.

In either case, the effect -is to counteract any tendency toward acontinuance of a departure from desirably balancedconditions. It is alsoseen that the system automatically adapts itself during these variationsto deliver a desired predetermined refrigerating effect tothe'rectifying column. For example, any reduction in volume of throttledgas admitted to the column at high pressure is offset by increasedpressure both in the throttled gas and-in the expanded gas deliveredfrom the expansion engine. The converse is equally true when the volumeof throttled gas is increased.

Referring now to the drawing and particularly to Fig. 1, 10 denotes afirst stage cylinder of a main compressor which effects a portion of thepreliminary compression of the gaseous medium to be supplied to a gasliquefying and rectifying apparatus, shown generally at 30, the gaseousmedium being supplied to the cylinder 10 by way of an inlet conduit 11which conveys the gaseous medium from any suitable source, for example,from the atmosphere when filtered and cleaned. The gaseous medium whencompressed in the cylinder 10 is discharged intoa second stagecompression cylinder 12, where the gaseous medium is further-compressed,after which it is discharged to a third cylinder 13, where another stageof preliminary compression is accomplished, and finally to a cylinder 14where a still further stage of compression is accomplished, the gaseousmedium being thereby raised to'a desired high pressure, for example, to140 atmospheres, or approximately 2100 pounds gage pressure in the caseof air. The pistons for the several stages of compression preferablyhave the same stroke but progressively decreased diameters, and are hereshown on a common crank shaft 15, which has a fly-wheel 16 belted orotherwise geared to be driven from an electric. motor 1'7. Interstagecooling is preferably practiced in connection with the conduits, whichconvey the compressed medium from one stage to another. For example,

conduit 18 is shown as leading from the outlet a coil 22 provides thecooling surface in the con.-

duit 21, which leads from the outlet chamber of cylinder 12 to the inletchamber of cylinder 13. Similarly, a coil 24 provides cooling surface inthe conduit 23, which leads from the cylinder 13 to the cylinder 14. Aconduit 25 having a cooling coil 26 is arranged to convey the gaseousmedium now at the desired pressure and temperature tov the second partof the compression machinery.

The compression machinery to which the conduit 25 leads comprises acylinder 27 for accomplishing further compression of the gaseous mediumand boosts the pressure to a still higher value, for example, to apressure of 200 atmospheres or approximately 3000 pounds gauge in thecase of air. The compressed medium at this highwhile the other isconveyed through conduit 31 to a cylinder 32, where expansiontakes placeby doing external work and is then supplied through the conduit 33 inparallel with that portion supplied through conduit 29 to the column 30.The desired quantity ratio to be generally maintained between the twoportions is determined firstly, by the displacement of the expan sionengine; secondly, by the time during which the inlet valve of thisengine is open; and thirdly, by the opening of the expansion valve 29".For example, in the case of air, it is usually preferable that theexpansion engine be of such capacity that it will expand of thecompressed air from the pressure of 3000 lbs. gage to the columnpressure of '75 lbs. gage for the production of the desired relativelylarge quantity of relatively lower quality refrigeration and thattherefore 60% of the air will pass through conduit 29 to be precooled toa relatively low temperature by exchanger 29' and expanded through theexpansion valve 29" to obtain the desired high quality refrigerationwithin the column 30. The expansion means which thus does internal workwith the compressed medium and the expansion engine which does externalwork, operate in parallel and finally expand the medium to a relativelylow pressure, for example, to a pressure of 5 atmospheres in the case ofair, i. e., the medium thus expanded is supplied to column 30 atapproximately '75 pounds gage pressure. It will be noted that thegaseous medium is here expanded in the expansion engine to a pressurematerially lower than thepressure at which it is Supplied to thecompression cylinder 2'7.

in order that the expansion engine having cylinder 32 may do usefulwork, in accordance with the invention, this engine is coupled to drivethe boosting compressor at 2'7. Any suitable mechanical connections thatallow the expansion cylinder to operate expansively after admission cutofi may be employed, for example, a system in which the pistons of theexpansion engine and boosting compressor are connected by connectingrods 34 and 35, respectively, to a common crank 36, which has afly-wheel 3'7. By this arrangement, the external work which the gaseousmedium does in driving the expansion engine is transmitted to theboosting compressor 2'7. Column 30 is shown as provided with outletconnections 39 and 40, from which liquid and gaseous products arewithdrawn, respectively, for example,

, ated. In this manner, substantially all the work done by, the engine32 is usefully employed in accomplishing the elevation of the gaseousmedium to a higher pressure.

Where the refrigeration load tends to vary between very wide limits orwhere changes inthe load to be normally carried are to be accommodated,it may be desirable also to provide manual adjustment for the admissionvalve mechanism. This may be conveniently provided in connection withthe valve gear on shaft 41, that connects the crank 36 with the flywheel3'7. This gear is shown in Fig. 2 as comprising a cam 42 that actuates areciprocating rod 43 having a cam wheel or roller 44 mounted in its endand bearing on the cam 42. The other end of this reciprocating rod hasan articulated portion 45 which makes variable engagement with a valveoperating lever 46, the latter being pivoted at 47 to operate a springclosed poppet valve 48 mounted in the head of the expansion engine tocontrol the admission of the compressed medium to be expanded. A valve49 is also shown in the head of cylinder 32 for controlling the outflowinto the conduit 33, and

is actuated in any manner desired. In order that the articulated portion45 may make variable engagement with the actuating lever 46, a camroller 50 is pivoted in its end which bears against 32, and has anoperating rod 54 which is moved in response to variations in such load;this movement may be eifected manually or automatically, a manuallymanipulated nut 55 being here shown for locking the rod. 54 in place.

In operation, it is seen that the gaseous medium which is to becompressed, cooled and expanded, is drawn in from the atmosphere throughthe conduit 11 to the main compressing stages, where a desired highpressure is obtained, the energy for driving these compressing stagesbeing delivered by the motor 1'7. The compressed gaseous medium whichhas been subject to interstage cooling then passes through conduit 25 tothe boosting compressor 27, after which it is divided into two portions,in accordance with the predetermined ratio, one portion passing by wayof the conduit 29 through heat exchanging means 29' where it ispre-cooled by thermal contact with a cold product and through thethrottling valve "29" into the column 30, while the other portion ispassedby way of conduit 31 to the expansion engine 32, where thecompressed gaseous medium delivers its energy to do external work anddrive the boosting compressor 27, after which it is supplied throughconduit 33 to the column 30; these portions being utilized together toaccomplish the liquefaction and/ or separation of gas in an economicalmanner in the column 30. Here, it is seen that the two expansion means,the first of which does internal work on the gas, while the second doesexternal work, operate inparallel.

The proportion of high quality refrigeration to low quality-largequantity refrigeration may be changed through a relatively moderaterange by adjusting the degree of opening of the inlet valve 48 on theexpansion cylinder. Thus to effect an increase of this ratio, thearticulated portion of the-rod at 45 is moved outwardly from thecylinder head by causing the rod 54 to move inwardly. Thus, it is seenthat the actuating stroke of the lever 46 is reduced, so that the inletvalve 48 admits less compressed medium to be expanded. Consequently,less power is generated in the expansion. cylinder, so that the enginewill slow down slightly until a new balanced condition is reached. Inpractice, it is seldom necessary to adjust the ratio by means of theadjusting rod 54, as the fine adjustments to the demand forreirigeration are obtainable with the valve 29", as well asautomatically, as above described.

In a system of the present invention,. a bal-' anced condition is alwaysautomatically reached both when the proportions of air flowing arechanged as described above and when there is any change in therefrigeration load such as would be caused 'by slight obstructions atthe expansion valve 29". It will be readily seen that a new balancedcondition is automatically reached, since by reason of the mechanicalcoupling of booster to expander, the constant rate at which gas isdelivered from the initial compression to the boostenand the greaterratio of variation in booster work as compared with expander power withany given change in speed, any tendency for the speed of the expansionengine to change is immediately taken up by the booster so that itadjusts itself and the power produced is equal to the power consumed. Inthe case of air, the ratio of expansion in the engine is the ratio ofcompression in the booster is a proximately v If the throttlingvalve 29"should be closed slightly as by a slight obstruction, there is atendency for the pressure in conduit 31 to rise. If, for example, thispressure rises from 3000 to 3100, slightly more air will expand througha slightly increased expansion ratio, i. e.

Consequently, the power output increases slightly and the speed wouldtend to increase. But at the booster cylinder, the mass per unit of timeof air handled is constant while the compression ratio change is atfirst booster will tend to fall off at a greater rate, thus preventingthe slowing down. Friction can be neglected as it is practicallyconstant within the range of operating conditions considered.

-I The inherent balancing tendency is the more positive when all the airpasses through the booster cylinder and only apart of the air isexpanded in the expansion-engine, for then the expansion ratio can besufflciently greater than the compression ratio ofthe; booster. For existhrown upon the main compressor.

- cooling and is not far from ample, when the proportion of air expandedthrough the expansion valve is 60% to 40% expanded in the engine, theinherent stability of the system :is very great.

When the power output of the engine is de- 6 creased-by decreasing thedegree of opening of the expansion cylinder inlet valve, i. e., byproviding an earlier cut-off, the engine tends to slow down, thusdecreasing the displacement of the booster cylinder so that it canhandle only 10 a smaller volume of air, but since the quantity or massper unit of time of air being delivered by the main compressor ispractically constant, the pressure in conduit 25 of air entering thebooster will rise so that its volume is decreased to a value equal tothe decreased displacementv of the booster. Compression, therefore,occurs through -a smaller compression ratio and less power is used bythe booster, while more work The use of a coupled booster-expander ashere proposed permits more economical starting. At the beginning of,operation, it is desirable to speed up the cooling of the apparatus andthe condensing of considerable air which are prerequisite torectification. Therefore, at the beginning it is necessary to provide arelatively great refrigerating eflfect even at the expense of highquality. This is accomplished in practice by passing a relativelylargequantity of air through the engine until the apparatus reaches theexhaust temperature of the engine, then switching to the ratio of engineexpanded to throttled air which gives a desired Joule-Thomson the usualoperating point.

Since the dimensions of the expansion engine are fixed, increasing theamount of air to the engine results in lowering the ratio of expansionand increasing the pressure and temperature at 40 the point of exhaust,and the temperature of the exhaust gas leaving the engine. Inthe'boosterexpander the speed increases with the "larger cut-off, sothat the cut-01f does not have to be quite so great to handle a definiteincrease in volume. Consequently, the exhaust temperature of thebooster-expander engine is lower than that of av constant speed engine.Thus, during the first period of starting up, more heat is removed perpound of gas processed, and also the first period is continued toslightly lower temperature which is more economical because en- 'ginecooling is more efiicient than Joule-Thomson cooling.

The stabilization effect operates to neutralize substantially anydisturbance arising because of the fact that the opening at the orificeof valve 29" changes slightly from hour to hour. Such changes areproduced by carbon dioxide snow and possibly some water snow forming on.and 0 then flaking off the valve. When, due to flaking off of suchsnow, a slight additional opening of the valve 29 occurs in a cycle inwhich an expansion engine runs at constant speed, the

head pressure falls, and since the amount of 5 air through the expansionengine is directly proportional to the suction pressure and the speed,it also fails. Thus the ratio of the amount of engine expanded air tothrottled air may fall markedly. However, in the case of theselfgoverning booster-expander, a drop in the high pressure, causesthe'engine to speed up since the ratio of compression is decreased morethan the ratio of expansion. This increase in speed compensategfor thedecrease in pressure. Both paths for the air, that is, those throughconduits 31 and 29 respectively, are opened, and the ratio of engineexpanded to throttled air is maintained more nearly constant. Thisconstant ratio of high to expanded air which is obtained by the use ofthe booster-expander has a marked efiect in securing a stable operation.

The boosting compressor and expansion engine may be designed from theengineering data generally applicable to machines of their kind. Thevolume of gaseous medium to be handled through the two machines beingassumed, together with the pressure change across each, the boosting,compressor and expansion engine can be built of such size as to run atany predetermined speed. The highest pressure in the system, which isreached between the boosting compressor and the expansion engine, is animportant datum, and must be of the proper degree in order that thesystem may operate as intended. The system has been proved to beinherently stable, and if the piston displacement of the boostingcompressor, and that of the expansion engine are of the propermagnitude, all pressures and speeds remain substantially constant attheir intended values. I

Since certain changes may be made in, the above construction anddifierent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawing shall beinterpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secureby Letters Patent, is: 1. The method of compressing and expanding agaseous medium to produce a liquefied gas which ternal work in effectingsaid further compres sion, and automatically maintaining the volume ofthe medium liquefied substantially constant when the ratio of theportion expanded internally to that expanded externally changes.

2. The method of compressing and expanding a gaseous medium to produce aliquefied gas which comprises compressingthe gaseous medium at asubstantially constant rate by means of energy independently supplied,further compressing the compressed medium at a rate which may vary,cooling the compressed medium by heat exchange, engine expanding atleast a portion of the compressed medium, utilizing the energy obtainedfrom said engine expansion to do the work of saidfurther compression,throttle expanding the remaining portion of the compressed medium, andcounteracting the efiect of an interference with the rate of throttleexpansion to change the volume of gaseous medium liquefied by changingthe rate at which said work is done.

3. The method of compressing and expanding a gaseous medium to produce aliquefied gas .which comprises compressing the gaseous medium at achange, dividing said cooled compressed medium into two parts inaccordance with a desired ratio, effecting throttling expansion of oneof said parts, engine expanding the other part, utilizing the energyobtained from said engine expansion to do the work of said furthercompression, and automatically changing the rate at which said externalwork is utilized in response to changes in the rate at which saidthrottling expansion takes place whereby the volume of the mediumliquefied remains substantially constant.

4. The method of compressing and expanding air in a system havingcompression devices arranged in series and expansion devices arranged inparallel for producing a refrigerating efiect .which comprisescompressing the air drawn from the atmosphere at a substantiallyconstant rate, cooling the same by heat exchange, further compressingthe cooled compressed air at a rate determined by a predeterminedpressure difierential in the system, further cooling the same by heatexchange, dividing said further cooled compressed air into two portionsin accordance with a predetermined ratio, further cooling one of saidportions by causing the same to expand and to do internal work, furthercooling the other of said portions by expanding the same and causing thesame to do external work, the ratio of expansion for said last-mentionedportion being substantially greater than the ratio of compressionaccomplished when effecting said step of further compression, supplyingenergy independently to accomplish the compression at said constantrate,

applying the energy released by having one of said portions do externalwork for accomplishing the step of said further compression, andcompensating any tendency to change the ratio of the portion expanded bydoing internal work by a correlated tendency in the portion expanded bydoing external workwhereby the volume of liquefied medium producedremains substantially constant. g 1

5. The method of compressing and expanding a gaseous medium to produce arefrigerating effect which comprises supplying independently the energyfor efiecting the step of initially raising the pressure of a gaseousmedium from an initial low-pressure to a relatively high pressure,cooling the same by heat exchange, boosting the pressure of saidcompressed medium to a still higher pressure, again coolingv the mediumby heat exchange, dividing said compressed medium into two portions andexpanding the same in parallel by causing the same to do internal andexternal work respectively, applying the energy released in doingexternal work to accomplish the step of boosting the medium to saidhigher pressure, and utilizing a variation in pressure which is afunction of said boosting compression to determine the relative amountsof energy to be applied in efi'ecting said boosting compression withrespect to said initial compression whereby tendencies to variation inthe efiect desired'are counteracted.

6. The method of delivering compressed cooled air to a rectifyingcolumn, which comprises preliminarily compressing and cooling input air,further compressing at least a portion of said input air, indirectlycooling said further compressed air, expanding at least a portion ofsaid input air with internal work through a throttle valve into thecolumn, expanding at least a portion of said input air with externalwork through an expansion engine intothe column, utilizing said externalwork for said further compressingqmd automatically maintaining thevolume and refrigerating effect of input air to the column substantiallyconstant despite fluctuation in the ratio of input throttled air tototal input, air.

7. The method of producing refrigeration in a system having compressiondevices and engine expansion and throttling expansion devices inparallel for processing air supplied to a rectifying column, whichcomprises compressing air drawn from the atmosphere to a desired highpressure by means of energy obtained from an external source, boostingthe pressure of said compressed air by means of energy obtained from theengine expansion of a portion of said compressed air, eifectingthrottling expansion of the remaining portion of said boosted compressedair, and proportioning the expansion ratio by which said engine expandedair is expanded to the compression ratio by which the boosting of saidcompressed air is efiected to have a value such that any tendency forthe total air and refrigeration input to the column to vary, on accountof some interferences with the free flow of throttled air to the column,is compensated for and a self-balancing system is obtained.

8. The method of producing refrigeration in a system having compressionand expansion devices arranged to process air supplied to a rectifyingcolumn, which comprises initially compressing air to a desired highpressure, thereafter boosting all of said compressed air to a stillhigher pressure, dividing said boosted compressed air into a pluralityof portions, causing one of said portions to expand and do internalwork, causing another of said portions to expand and do external work,utilizing said external work to effect said boosting compression, andproportioning the expansion ratio of doing external work to the ratio ofthe boosting compression so as to have a value such that any tendencyfor the total air and refrigeration input-to the column to vary, onaccount of interference with internal work, is compensated for over therange of normal operation.

' 9. The method of producing refrigeration in a system havingcompression devices arranged in series and expansion devices arranged inparallel to process air supplied to a rectifying column,

which. comprises compressing the air in said se-- ries of compressiondevices to successively higher pressures, providing independently theenergy for ation input to the column to change, dueto changes in theexpansion accomplished by said internal work expansion devices over thenormal range of operation is compensated for, and manually adjusting theexternal work expansion devices to accommodate changes which are beyondthe range of normal operation.

10. The method of producing refrigeration in a system having compressiondevices and engine expansion and throttling expansion devices inparallel for; processing air, which comprises compressing the air to adesired high pressure by -means of energy obtained from an externalsource, boosting the pressure of all of said compressed air by means ofenergy obtained from expansion of said compressed air, initially coolingsaid system by engine-expanding a greater than Y stantially normalproportion of said boosted compressed air, and when cooled to a desiredlow temperature simultaneously expanding in nomal proportion differentportions of said boosted compressed air by engine expansion andthrottling expansion respectively.

11. The method of producing refrigeration in a system having compressiondevices and engine expansion and throttling expansion devices inparallel for processing air, which comprises compressing the air to adesired high pressure by means of energy obtained from an externalsource,

boosting the pressure of all of said compressed air by means of energyobtained from expansion of said compressed air, initially cooling saidsystem by engine expanding a greater than normal proportion of saidboosted compressed air, and when said system is sufilciently cooled,switching to normal proportions the respective portions of said boostedcompressed air to be expanded by throttling expansion and engineexpansion in parallel.

12. In a system for producing refrigeration by processing atmosphericair, the combination comprising means for compressing intake air at asubstantially constant rate, a booster compressor arranged for operationat a variable speed for further compressing the compressed air, athrottling valve for expanding a portion of said further compressed air,an expansion engine for expanding another portion of said furthercompressedair in parallel to that expanded in said throttling valve,said expansion engine having a ratio of expansion substantially greaterthan the ratio of compression in said booster compressor, and amechanical coupling connecting said expansion engine to drive saidbooster compressor whereby said booster compressor and said expansionengine are able to absorb any tendencies to variation in the powerrequirements of said booster compressor when the flow of air throughsaid throttling valve is interfered with.

13. In a system for producing refrigeration by processing atmosphericair, the combination comprising main compressing means for compressingair drawn from the atmosphere, means for driving said maincompressor,-an additional compressor connected in series with said maincompressor for boosting the pressure of all of the air compressed insaid main compressor to a higher pressure, a throttling expansion deviceand an engine expansion device disposed in parallel, each arranged toreceive a portion of the air compressed to said higher pressure andsupplying the same to a common place where said refrigerating effect isproduced, means for coupling the engine expansion'device as the soledriving means to drive said boosting compressingmeans, and meansresponsive to a pressure variation which is a function of said boostingcompressor for determining the energy to be supplied respectively tosaid first named and to said second named driving means whereby tomaintain subconstant a desired effect at the place of use.

14. In a system for producing refrigeration, the combination with anapparatus for processing atmospheric air, having a main compressingmeans for initially compressing the air to a desired high pressure, ofadditional compressing means for boosting air compressed-in said mainengine means for expanding said air compressed in said system by doingexternal work and decreasing the pressure to a value less than saiddesired high pressure, means for conveying the air subsequent tocompression through said heat exchanger to a place of use, means forapplying the work or said engine expanding means to drive saidadditional compressing means, means for regulating the speed of saidengine expanding means, and power means for independently supplyingenergy to drive said main compressing means.

15. In a system for producing refrigeration, the combination with anapparatus for processing atmospheric air having a main compressing meanstor initially compressing the air to a desired high pressure, ofboosting compressing means for raising the compressed air to a higherpressure,

throttling expansion means, engine expansion means, means for dividingand conveying the air at said higher pressure from said boostingcompressing means to said throttling expansion means and to said engineexpansion means respectively into portions in accordance with apredetermined ratio, means vifor mechanically coupling said boostingcompressing means to said engine expansion means for utilizing the workdone by expansion, said engine expansionmeans having a relatively largeexpansion ratio and said -boosting compressing-means a relatively smallcompression ratio, whereby said coupled boosting compressing means andthe engine expansion means are inherently capable of absorbingtendencies for speed variation due to variation of pressure on theintake side or saidboosting compressing means. 7

16. In a system for producing refrigeration, the combination with anapparatus for processing atmospheric air having a main compressing meansfor initially compressing the air to a desired high pressure, ofboosting compressing means for raising the compressed air to ahigherpressure, a heat exchanger for receiving the air from said boostingcompressing means, engine expansion means for expanding a portion ofsaid boosted compressed air, throttling expansion means for expandinganother portion of said boosted compressed air, means for dividing theair received from said heat exchanger into two portions inaccordanceiwith a predetermined ratio, engine expansion means forexpanding one or said portions, throttling expansion means for expandingthe otherot said portions, means tor mechanically coupling said engineexpansion means to drive said boosting compressing means, said coupledboosting compressing means and engine expansion means having theirrespective displacement ratios relatively proportioned so as to providea system capable oi compensating for any tendency to variation v due tochanges in the amount of air being processedby, throttling expansionover the normal operating range, means for regulating the speed of saidengine expansion means beyond the normal range ot'variation, and

power means for independently supplying energy' to drive said maincompressing means.

17. In a system for producing refrigeration by processing air, thecombination comprising a main compressing means for compressing air at asubstantially constant rate, additional compressing means for boostingthe pressure operating at a variable rate, means for effectingthrottling expansion or a portion of the air, the pressure of which hasbeen boosted, means for eiIecting engine expansion of another portion orsaid boosted compressed air arranged to operate in parallel with saidthrottling expansion means. said engine expansion means normallyeffecting expansion by 'a greater ratio than the ratio oi compression insaid additional compressing means, and a coupling arranged to transmitdriving energy from saidengine expansion means to said additionalcompressing means whereby the coupled means absorbs any tendency tovariation in the power requirements of said additional compressing meanswhen additional resistance develops to the flow of air through saidthrottling-expansion means. I

. HARRY D. EDWARDS.

